Electric vehicles that run on driving power of electric motors and hybrid vehicles that run on both internal combustion engines and electric motors are each mounted with a battery module, as its power source device, in which a large number of batteries are provided. As the battery module, an example thereof is disclosed in JP 4815026 B. FIG. 12 shows a cross sectional diagram of the battery module disclosed in JP 4815026 B. As shown in FIG. 12, the battery module includes a housing 950 with a lid 920, a plurality of batteries 940 housed inside the housing 950, and a bus bar module 930 disposed at one end side of the plurality of batteries 940. The bus bar module 930 is disposed between a housing chamber 990 for housing the batteries 940 within the housing 950 and a gas discharging chamber 924 in the lid 920 so as to seal the housing chamber 990. The plurality of batteries 940 is connected in parallel by the bus bar module 930 with their positive electrode caps 916 oriented toward the one end side where the bus bar module 930 is disposed. The bus bar module 930 includes a laminated plate 931 in which a heat resistant member 930a and an elastic member 930b are laminated, and a conductive connector 932 formed on a surface of the laminated plate 931. The positive electrode caps 916 are inserted in through holes 936 formed in the laminated plate 931. The positive electrode caps 916 are connected to the connectors 932.
In a lithium ion battery, sudden heat generation may take place by overcharging, over-discharging, short circuiting, and the like. In this case, an internal pressure inside the batteries may rise due to air expansion inside of the battery or generation of volatile gas from electrolytic solution, and there is a fear of resulting in a breakage. Due to this, the lithium ion battery is provided with a valve for releasing the gas upon when the internal pressure rises. In a case where the lithium ion battery has a cylindrical shape, the valve is provided at an end of this cylindrical-shaped battery in an axial direction. In an in-vehicle battery module, the housing chamber 990 is communicated with a vehicle compartment, and the gas discharging chamber 924 is communicated with outside of the vehicle. While the gas generated from the battery is caused to flow into the gas discharging chamber 924, the interval between the end of the battery 940 and the bus bar module 930 is sealed so that no gas leaks out to a driver's seat, and the housing chamber 990 is isolated from the gas discharging chamber 924.
However, the bus bar module 930 described in JP 4815026 B has a two-layer structure in which the heat resistant member 930a and the elastic member 930b are laminated, and the structure is thereby complicated.
Thus, the inventor has conducted keen investigation to develop a bus bar module with a simple configuration. During the development of the bus bar module, it was considered to insert molding a bus bar formed of a metal thin plate with a polymeric material. However, a thermal expansion coefficient of the metal bus bar is smaller than a thermal expansion coefficient of the polymeric material. Due to this, the polymeric material may shrink after the molding and an entirety of the bus bar module may warp, and the interval between the end of the battery and the bus bar module may not be sealed surely. In such a case, if the battery generates gas due to overcharging, over-discharging, internal short circuiting, or external short circuiting, the gas is discharged from the end of the battery 940 into the gas discharging chamber 924. If there is a gap between the end of the battery 940 and the bus bar module 930, the gas may leak out to the housing chamber 990 and the external periphery of the housing 950 from the gas discharging chamber 924 through the gap, and the gas may be directed into the vehicle compartment.
Further, there also is a desire to be able to absorb assembly discrepancy of the battery and the like by the bus bar module 930 by preventing the warping of the bus bar module.
To solve this problem, JP 2012-236325 A proposed fitting a stainless sheet in which a slit is formed into a cavity of a molding die and pouring molten resin therein, so that the shrinking upon the cooling of the molten resin can be alleviated by the slit.
However, the rigidity of the stainless sheet lowers due to the slit.